Ventricular assist devices (VAD) pump blood in parallel with the native ventricles of the human heart. This provides blood flow to the body when the patient's own heart is in failure. A typical implantation of a VAD in the left side configuration takes blood from the apex of the left ventricle and returns blood to the ascending aorta at higher pressure. The VAD thereby takes on a significant portion of the work done by the native heart without removing the native heart.
VADs are at times used in temporary applications, such as bridge to heart transplantation or bridge to recovery of the native heart. However, the largest application of VAD's is likely to be long-term use of the device through the duration of the patient's life. This is also known as destination therapy (DT) use of the device.
There are several commercially available VAD systems that use batteries to power the controller and pump. These include the Thoratec HEARTMATE I® and HEARTMATE II®, from Thermedics, Inc. the WorldHeart Novacor® system, from WorldHeart Corporation, and others. Generally, these systems are required to have two sources of power to be able to operate safely. Previous systems have been implemented with two external batteries, or one external battery and a power supply from the AC mains that must be connected to the patient and all times.
Totally implantable systems have been developed to the research or commercialization stage that include a bridge battery and an external power source supplied through a transcutaneous energy system. These systems include Implantable heart assistance devices from ARROW LIONHEART™, from Penn State College of Medicine, the Jarvik 2000 ®, from Jarvik, and the Abiomed AbioCor® Total Artificial Heart, from Abiomed, Inc. None of these systems apply the reserve battery concept to an externally wearable controller.